This invention relates to semiconductor wafer processors, plasma generating apparatus, magnetic field generators, electric motors, and to methods of generating magnetic fields.
Plasma discharges are widely used in semiconductor wafer processing to modify the surface properties of materials. A plasma is a collection of free charged particles moving in random directions that is, on the average, electrically neutral. Plasmas can be chemically reactive or inert, and among other things are utilized to either deposit or etch materials from a substrate surface such as semiconductor wafer.
Magnetically enhanced plasma discharges are utilized, for example, to increase plasma density and to reduce voltage at the sheath of the plasma for a given power. A magnetic field can facilitate confinement of the ionizing electrons to a small volume near the surface of a semiconductor wafer. Although magnetically enhancing a plasma discharge can result in reduced sheath voltage and increase plasma density, many prior art generated plasmas are strongly non-uniform radially and azimuthally. Such results in less than desirable process uniformity. It has been proposed that to increase process uniformity, at least azimuthally, the magnetic field can be rotated in the plane of the wafer at a low frequency, but this apparently has not met with much success.
It would be desirable to develop improved methods and apparatus for generating a magnetic field associated with semiconductor wafer plasma processors and processing. While commercially motivated from this primary objective, the reader will appreciate applicability of the invention in other art areas, with the invention only being limited by the accompanying claims appropriately interpreted in accordance with the doctrine of equivalents.